(1 of )In this Oct. 22, 2017 file photo, San Francisco 49ers linebacker Reuben Foster stands on the sideline during the second half of against the Dallas Cowboys in Santa Clara. (AP Photo/Marcio Jose Sanchez, File)

(2 of )San Francisco 49ers outside linebacker Reuben Foster (56) against the Los Angeles Rams during the first half of an NFL football game Sunday, Dec. 31, 2017, in Los Angeles. (AP Photo/Rick Scuteri)

(3 of )Jacksonville Jaguars wide receiver Keelan Cole (84) runs against the San Francisco 49ers during the first half of an NFL football game in Santa Clara, Calif., Sunday, Dec. 24, 2017. (AP Photo/Tony Avelar)

(4 of )San Francisco 49ers linebacker Reuben Foster (56) against the Jacksonville Jaguars during the first half of an NFL football game in Santa Clara, Calif., Sunday, Dec. 24, 2017. (AP Photo/Marcio Jose Sanchez)

Grant Cohn: Reuben Foster hurt himself and 49ers with his immaturity

I like Foster. He’s intelligent, friendly, funny, almost always available to talk. Surprisingly normal and down to earth for a high-profile athlete. One of my favorite players to interview on the 49ers. And he loves to play football. And, man, can he play.

This isn’t about his ability or personality.

And this isn’t about weed. I’m not debating marijuana. That issue has been decided in California for Californians.

Foster wouldn’t even be in trouble had he stayed in California for the offseason. But he went back home to Alabama, and police charged him with second-degree marijuana possession fewer than two weeks after the 49ers’ final game of the season.

Foster wasn’t trafficking pounds of narcotics or anything serious. He had a small amount of weed for personal use. I’m not criticizing him for that.

I’m criticizing him for not knowing the reality of his job and the NFL. For not understanding grownup responsibility. For not being a good teammate, employee or adult.

Foster isn’t a college player any longer. He is a professional athlete, and being a professional involves choosing wisely in terms of behavior, and feeling responsible to teammates and the organization.

The 49ers hang a list of team rules on the wall of their locker room in Santa Clara. The No. 1 rule is “Protect the Team.” Foster broke that rule.

As long as the NFL prohibits the use or possession of marijuana, Foster has an obligation to everyone on the 49ers to stay clean. He must be willing to make that sacrifice. He needs to plan ahead and understand the meaning of his actions. That’s what being a professional is about.

General manager John Lynch and head coach Kyle Shanahan put their reputations on the line when they drafted Reuben Foster. They vouched for him.

Foster had failed a drug test at the NFL Scouting Combine. If he hadn’t failed, he probably would have been a top-five pick. Teams are reluctant to draft players who are in the NFL’s Substance Abuse Program, because those players are subject to random drug screenings and multi-game suspensions if they fail more tests.

Foster fell to the end of Round 1 of the draft, where the 49ers traded up to take him. Lynch and Shanahan believed Foster was a great value at that spot. Now, he’s making them look foolish for believing in him.

And, we’re starting to see why the rest of the league wouldn’t touch him.

In retrospect, it was a bad sign Foster couldn’t quit weed long enough to pass a drug test at the Combine, a test he knew was coming for a job that would pay him millions.

And it was a really bad sign that he chose to have a marijuana and tobacco vaporizer company sponsor his draft party even though he had failed a drug test.

This recent arrest probably was predictable.

Foster seems to have a problem with marijuana. He continually allows it to jeopardize his career and hurt him financially.

The NFL will fine Foster two game checks next season. This fine will void $2.5 million of guarantees in Foster’s contract with the 49ers. That certainly will get his attention.

Foster still can earn back that money, but he has to play to earn it. He won’t get paid for games he misses. And playing isn’t a given for him. Foster is injury prone. He missed six games last season.

He probably will miss at least one next season. NFL Network’s Ian Rapoport said the NFL most likely will suspend Foster for one game. That’s standard protocol for a player in Stage 2 of the NFL’s Substance Abuse Program.

If he fails another drug test, the NFL probably will suspend him two games. And then four games. And then 10 games. And then a full year. If Foster doesn’t quit smoking now, he’ll be out of the league in a year or two. He’ll be the next Aldon Smith.

Foster brought all this on himself.

Now, he’ll have to take random drug tests for as long as the league sees fit, stay sober, stay healthy, stay on the field and work for every penny he gets.

In a way, this may be good for Foster. This is his chance to think about the outcomes of his actions before he takes them.

This is his chance to grow up.

Grant Cohn covers the 49ers for The Santa Rosa Press Democrat and Pressdemocrat.com. You can reach him at grantcohn@gmail.com.